# std::char_traits<char>::eq/lt, std::char_traits<wchar_t>::eq/lt, std::char_traits<char8_t>::eq/lt, std::char_traits<char16_t>::eq/lt, std::char_traits<char32_t>::eq/lt

From cppreference.com
< cpp‎ | string‎ | char traits

static bool eq( char_type a, char_type b ); | (1) | (constexpr since C++11) (noexcept since C++11)
static bool lt( char_type a, char_type b ); | (2) | (constexpr since C++11) (noexcept since C++11)

Compares two characters.

1) Compares a and b for equality, behaves identically to

- static_cast<unsigned char>(a) == static_cast<unsigned char>(b), if `char_type` is char,
- a == b otherwise.

2) Compares a and b in such a way that they are totally ordered, behaves identically to

- static_cast<unsigned char>(a) < static_cast<unsigned char>(b), if `char_type` is char,
- a < b otherwise.

See CharTraits for the general requirements on character traits for `X::eq` and `X::lt`.

### Parameters

a, b | - | character values to compare

### Return value

1) true if a and b are equal, false otherwise.
2) true if a is less than b, false otherwise.

### Complexity

Constant.

### Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR | Applied to | Behavior as published | Correct behavior
--- | --- | --- | ---
LWG 467 | C++98 | for std::char_traits<char>, the semantics of `eq()` and `lt()` are the same as the built-in == and < on char respectively[1] | changed to built-in == and < on unsigned char

1. ↑ Most implementations call std::memcmp() for efficiency, which interprets the data as arrays of unsigned char. If char is signed on such implementations, std::char_traits<char> fails to satisfy the requirements of CharTraits.

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/string/char_traits/cmp&oldid=171371"